书目名称 | Progress in Motor Control | 副标题 | Skill Learning, Perf | 编辑 | Mindy F. Levin | 视频video | http://file.papertrans.cn/761/760585/760585.mp4 | 概述 | Written by an expert group of scientists and clinicians.Wide range of theoretical, as well as actual approaches.Addresses the mechanisms of typical motor control, plus deficits and disorders of moveme | 丛书名称 | Advances in Experimental Medicine and Biology | 图书封面 |  | 描述 | This volume is the most recent installment of the Progress in Motor Control series. It contains contributions based on presentations by invited speakers at the Progress in Motor Control IX meeting held in at McGill University, Montreal, in July, 2013. Progress in Motor Control is the official scientific meeting of the International Society of Motor Control (ISMC). The Progress in Motor Control IXI meeting, and consequently this volume, provide a broad perspective on the latest research on motor control in humans and other species. | 出版日期 | Conference proceedings 2014 | 关键词 | Motor control; Motor development; Motor learning; Perception-action; Sensorimotor neuroscience | 版次 | 1 | doi | https://doi.org/10.1007/978-1-4939-1338-1 | isbn_softcover | 978-1-4939-4825-3 | isbn_ebook | 978-1-4939-1338-1Series ISSN 0065-2598 Series E-ISSN 2214-8019 | issn_series | 0065-2598 | copyright | The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Science+Busines |
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,Motor Control: On the Way to Physics of Living Systems, |
Mark L. Latash |
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Abstract
We accept two axioms: (1) the central nervous system is a physical/physiological object, not a computational one, and (2) the neural control of natural voluntary movements is organized in a hierarchical way. At the top level of the hierarchy, referent values for a few salient, task-specific variables are reflected in a set of neural signals (possibly, subthreshold depolarization levels of neuronal pools). Further, as a result of a sequence of few-to-many mappings, these signals result in sets of activation thresholds of the alpha-motoneuronal pools for the many muscles involved in the planned movement. This scheme naturally results in synergies stabilizing the values (time profiles) of task-specific, salient variables. In this context, “synergies” are defined as covaried across repetitive trials adjustments within a redundant set of elemental variables that ensure stability of a performance variable to which they all contribute. Several consequences of this scheme have received experimental support in recent studies. In particular, a novel phenomenon of feed-forward motor control, anticipatory synergy adjustments, has been discovered. Another nontrivial prediction of this scheme is that transient perturbations are expected to lead to equifinality at the level of task–relevant variables, but not necessarily at the level of elemental variables. Results of two recent experiments have confirmed this prediction for multi-joint positional tasks and multi-digit force production tasks. These results provide direct support for the ideas of control with referent configurations organized into a hierarchical system.
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,Motor Control and Position Sense: Action–Perception Coupling, |
Anatol G. Feldman,Nabil Ilmane,Samir Sangani,Helli Raptis |
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Abstract
According to previous studies, muscles become active in response to deviations from a threshold (referent) position of body segments. To test the hypothesis that corticospinal pathways set and reset the referent position in a task-specific way, we evaluated corticospinal influences at wrist positions established before and after voluntary motion as well as before and after involuntary motion elicited by the sudden removal of a load. Although tonic electromyogram (EMG) levels at pre- and post-unloading wrist positions were different, the corticospinal influences and thus the referent wrist position remained the same. These influences and the referent position changed, however, when subjects voluntarily moved their wrists to the other position. Thus, referent control strategies underlying the two types of motor actions are fundamentally different. We also tested the hypothesis that somatosensory afferents inform the brain about the deviation (.) of body segments from the centrally set referent position, .. To identify the actual position (.) of body segments and form the position sense (PS), the central and afferent signals are combined. The PS rule was confirmed by demonstrating that: subjects are able to successfully reproduce involuntary changes in position elicited by sudden unloading of wrist flexors by making voluntary wrist movements; successfully reproduce elbow joint positions under different constant loads; subjects may not be aware of elbow flexion elicited by tendon vibration until a certain limit (no-motion illusion). In conclusion, . and . are additive components of PS and, contrary to conventional assumptions, PS is independent of sense of effort or efference copy.
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,Reconfiguration of the Electrical Properties of Motoneurons to Match the Diverse Demands of Motor Behavior, |
C. J. Heckman,Michael D. Johnson |
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Abstract
Though long considered simple “threshold and fire” cells, motoneurons are now known to exhibit a wide range of electrical states. These state changes are induced by the interactions between three types of inputs: neuromodulatory, inhibitory, and .-methyl-.-aspartate (NMDA)-mediated. Perhaps the strongest neuromodulators are serotonin (5HT) and norepinephrine (NE), which are released by axons descending from the brainstem. Motoneurons are densely covered in synapses from both systems. Local neuromodulatory systems within the spinal cord also have strong effects. Generally, these neuromodulatory systems greatly enhance the excitability of motoneurons, increasing their input–output gain. Local inhibitory inputs may be able to reduce motoneuron gain by deactivating the persistent inward currents that are so strongly facilitated by 5HT and NE. The glutamate NMDA receptor tends to induce oscillatory behaviors and has recently been demonstrated to be strongly present in adult motoneurons. We propose that the interactions of these inputs can induce three different states in motoneurons: integration, variable gain amplification, and oscillation. We further suggest that these states are matched to the following motor behaviors: posture, volitional movements, and locomotion.
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,The Regulation of Limb Stiffness in the Context of Locomotor Tasks, |
T. Richard Nichols,Jinger S. Gottschall,Christopher Tuthill |
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Abstract
Locomotion on ramped surfaces requires modulation of both pattern-generating circuits and limb stiffness. To meet the mechanical demands of locomotion under these conditions, muscular activation patterns must correspond to the appropriate functions, whether the muscles are serving as force generators or brakes. Limb stiffness is a critical mechanical property that determines how the body interacts with the environment, and is regulated by both intrinsic and neural mechanisms. We have recently investigated how pattern generation, stiffness, and proprioceptive feedback are modulated in a task-specific way using the decerebrate cat preparation. Our results confirm previous research using intact animals that during level and upslope walking, hip and ankle extensors are recruited for propulsion during stance. During downslope walking, hip extensors are inhibited and hip flexors are recruited during stance to provide the needed braking action. Our new data further show that endpoint stiffness of the limb is correspondingly reduced for walking down a slope, and that the reduction in stiffness is likely due to an increase in inhibitory force feedback. Our results further suggest that a body orientation signal derived from vestibular and neck proprioceptive information is responsible for the required muscular activation patterns as well as a reduction in limb stiffness. This increased compliance is consistent with the function of the distal limb to cushion the impact during the braking action of the antigravity musculature.
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,Subcortical Visuomotor Control of Human Limb Movement, |
Brian L. Day |
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Abstract
It is generally accepted that cortical networks play a major role in the visual guidance of human limb movements. However, there is a growing body of evidence that points to subcortical visuomotor processes also having an important role to play. Behavioural evidence in man comes from studies on the very fast responses that occur when a target unexpectedly jumps to a new location during either an upper-limb reaching movement or a lower-limb stepping movement. In both cases, the target jump evokes a correction in the movement trajectory at a surprisingly short latency of 120–160 ms. These very fast reactions have a number of properties that are compatible with subcortical control: (1) they are not abolished by effort of will, (2) they can be made even faster by a startling auditory stimulus, (3) they do not obey Hick’s law. Further evidence comes from measurements of reach adjustment latencies in a subject with agenesis of the corpus callosum. Latencies are the same irrespective of whether the visual stimulus appears in contralateral or ipsilateral hemispace, a finding that is incompatible with cortical visuomotor control.
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,Rethinking the Role of Motor Simulation in Perceptual Decisions, |
Scott T. Grafton MD,Shivakumar Viswanathan PhD |
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Abstract
For decades, motor simulation has been invoked as a mechanism that utilizes covert output of the motor system to solve cognitive problems, including perceptual decisions. Evidence for motor simulation is based on indirect behavioral attributes including biomechanically constrained reaction times, the influence of the physical position of the participant’s limbs on performance, and a subjective sense of motion. Here, we propose that a large set of perceptual judgment experiments, where images of hands are used as stimuli and that have these behavioral attributes, are not based on motor simulation. We propose a fundamentally different mechanism for the effects observed in hand judgment: the multisensory binding of a mismatched seen hand with an unseen felt hand. Both hands are interpreted as belonging to the participant and obligatory coregistration of their positions into a single internal representation of body state causes the response delay, irrespective of the perceptual discrimination of hand laterality. Support for this alternative view is based on novel variations of the laterality task that manipulate local perceptual features to control binding. Multisensory integration is automatic, orientation dependent, and biomechanically constrained. The multisensory model eliminates conceptual inconsistencies that arise when motor simulation is invoked in this task. Finally, the multisensory binding model predicts the observed reaction time delays during hand judgments in a broad range of patients who have a distorted body schema. The new model questions the role, if any, of motor simulation in perceptual decision making and emphasizes the need for stronger experimental evidence to establish that motor simulation is occurring.
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,Use of the Uncontrolled Manifold (UCM) Approach to Understand Motor Variability, Motor Equivalence, and Self-motion, |
John P. Scholz,Gregor Schöner |
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Abstract
We review the uncontrolled manifold (UCM) approach to the analysis of motor variance. In that approach, variance in multi-degree of freedom systems is decomposed into variance that leaves task variables invariant (UCM) and variance that does not (orthogonal to UCM). Larger variance within the UCM than orthogonal to it is interpreted as evidence for a task-specific solution of the multi-degree of freedom problem. The extent to which UCM measures depend on the choice of variables and coordinate systems has been a topic of controversial discussion. We clarify these issues and explain the sense in which the UCM approach is geometric in nature. We embrace a combined approach in which the geometrical perspective is retained but complemented by an assessment of the correlations in multi-degree of freedom movement data. We then review the problem of motor equivalence, in which deterministic rather than stochastic perturbations probe the organization of multiple degrees of freedom. We argue that motor equivalence requires a UCM perspective because the effect of perturbations on the task variable cannot be compared to their effect on task-irrelevant dimension of the system unless both are embedded in a shared space. The geometrical interpretation of UCM is thus critical for this extension of the UCM approach. We finally briefly review the concept of self-motion that is likewise based on the geometrical view of UCM.
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,Acquisition of Novel and Complex Motor Skills: Stable Solutions Where Intrinsic Noise Matters Less, |
Dagmar Sternad,Meghan E. Huber,Nikita Kuznetsov |
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Abstract
Most experimental paradigms in motor neuroscience have used relatively focal and experimentally constrained tasks to allow precise measurement and experimental control. Therefore, practice-induced improvements and learning have been confined to relatively simple changes or adaptations to external perturbations. Here, we propose an approach to study more complex skills that are novel and require more extensive practice, leading to quantitative and qualitative changes in overt performance. Central to these skills is that they have extrinsic redundancy that allows exploration and exploitation of dynamic properties of the task. We hypothesize that in such skills, humans seek stable solutions that are robust to perturbations that make their intrinsic noise matter less. Three experimental paradigms exemplify our model-based and hypothesis-driven approach to skill acquisition: discrete throwing, rhythmic ball bouncing, and complex object manipulation. In skittles, a throwing skill, results show that actors are sensitive to the error tolerance afforded by the task. In ball bouncing, we show that subjects exploit the dynamic stability of the task, where small errors and noise self-stabilize without explicit corrections. In manipulating a “cup of coffee,” subjects learn to optimize the safety or energy margins and scale it to their intrinsic variability. This research presents new experimental paradigms that characterize the behavioral correlates of neuroplasticity in more complex skill acquisition. This fundamental work is a platform for future work to develop behavioral interventions for clinical applications.
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,The Dynamical Analysis of Inter-Trial Fluctuations Near Goal Equivalent Manifolds, |
Joseph P. Cusumano,Joseph M. Mahoney,Jonathan B. Dingwell |
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Abstract
Using the concept of task manifolds, a number of data analysis methods have been used to explain how redundancy influences the structure of variability observed during repeated motor performance. Here we describe investigations that integrate the task manifold perspective with the analysis of Inter-Trial task dynamics. Goal equivalent manifolds (GEMs), together with optimal control ideas, are used to formulate simple models that serve as experimentally testable hypotheses on how Inter-Trial fluctuations are generated and regulated. In an experimental context, these phenomenological models allow us to show how error-correcting control is spatiotemporally organized around a given GEM. To illustrate our approach, we apply it to study the variability observed in a virtual shuffleboard task. The geometric stability properties of the Inter-Trial dynamics near the GEM are extracted from fluctuation time series data. We find that subjects exhibit strong control of fluctuations in an eigendirection transverse to the GEM, whereas they only weakly control fluctuations in an eigendirection nearly, but not exactly, tangent to it. We demonstrate that our dynamical analysis is robust under coordinate transformations, and discuss how our results support a generalized interpretation of the minimum intervention principle that suggests the involvement of competing costs in addition to goal-level error minimization.
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,Motor Control in Action: Using Dance to Explore the Intricate Choreography Between Action Perception and Production in the Human Brain, |
Emily S. Cross,Anastassia Elizarova |
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Abstract
When experienced dancers watch other dancers perform, they perceive the movement in a quantifiably different manner than nondancers. Is this simply a matter of dancers paying more attention and having greater interest in watching dance, or do quantifiable differences exist within the brains of skilled dancers compared to nondancers related to years of physical practice? Previous neurophysiological research offers insight into this question through the discovery of specialized cells in the monkey brain that are active in a similar manner when monkeys perform or observe the same movement. This discovery of so-called mirror neurons established the idea of a close correspondence between action perception and production. Since this discovery, myriad studies have focused on the relationship between action production and perception in the human brain by studying the execution and observation of simple finger or hand movements. Work with dancers, however, extends such investigations to the full-body domain and helps to uncover how individual experience shapes the links between watching and performing actions. Much of this research uses neuroscientific methods to advance understanding of not only the cerebral phenomena associated with complex action learning and observation but also the neural underpinnings of aesthetic appreciation when watching dance. The results of this work are starting to inform and mutually benefit both the scientific and artistic communities.
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,Apollo’s Curse: Causes and Cures of Motor Failures in Musicians: A Proposal for a New Classification, |
Eckart Altenmüller M.Sc., MA, DiS,Christos I. Ioannou MSc, MA,Markus Raab PhD.,Babett Lobinger PhD |
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Abstract
Performing music at a professional level is probably one of the most complex of human accomplishments. Extremely fast and complex temporo-spatially predefined movement patterns have to be learned, memorized, and retrieved with high reliability in order to meet the expectations of listeners. Performing music requires not only the integration of multimodal sensory and motor information and its precise monitoring via auditory and kinesthetic feedback but also emotional communicative skills for a “speaking” rendition of a musical masterpiece. To acquire these specialized auditory–sensory–motor and emotional skills, extensive training periods over many years are a prerequisite, starting in early infancy and passing through stages of increasing physical and strategic complexities. Performance anxiety, linked to high societal pressures, fear of failure, and heightened self-demands is a frequent accompaniment of these learning processes..Motor disturbances in musicians are not uncommon and include mild forms, such as temporary motor fatigue with short-term reduction of motor skills, painful overuse injuries following prolonged practice, anxiety-related motor failures during performances, such as choking under pressure, and more persistent losses of motor control, here termed “dynamic stereotypes.” Musician’s dystonia, characterized by the permanent loss of control of highly skilled movements when playing a musical instrument, is the most grave manifestation of dysfunctional motor programs, frequently linked to a genetic susceptibility to develop such motor disturbances..In this chapter, we propose a new classification of motor failures in musicians based on the different degrees of “motor” or “psychological” mechanisms involved in the development of these disturbances. We argue that motor failures in musicians develop on a continuum, starting with subtle transient degradations, due to fatigue, overuse, or performance stress, which by and by transform into more permanent, still fluctuating motor degradations, the dynamic stereotypes, until a more irreversible condition, musician’s dystonia manifests. This new classification has implications for specific prevention strategies and for a client-tailored treatment.
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,Motor Control and the Injured and Healthy Artist, |
Roger M. Hobden MD,Samuel Tétreault |
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Abstract
Art is present in all aspects of life. An artless existence is inconceivable. Each of the many art forms requires specific training that will lead to the mastery of high-level performance. Dance is usually taught in the dance class where individualization of training is nonexistent. Circus artists are more specialized artists and individualization is central to the acquisition of circus motor skills. Skill acquisition is dependent on improving different qualities of motor performance relative to the task and, in particular, movement coordination. On the other hand, injuries that lead to inflammation hypermobility, hypomobility, pain, loss of strength, and loss of proprioception interfere with performance. Due to their heightened body awareness, artists can guide health professionals by describing their pain and functional limitations very precisely and accurately. Treating artists may lead to insights in the treatments of the general population.
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,Adaptations to Neck/Shoulder Fatigue and Injuries, |
Julie N. Côté PhD |
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Abstract
Musculoskeletal disorders (MSDs) of the neck/shoulder region affect a large portion of the population, in particular, people who perform upper limb repetitive motions as part of their occupation. Although some risk factors have been identified, much remains unknown about the etiology of neck/shoulder MSD. The way that people move and use their muscles, especially when performing repetitive upper-limb tasks that can cause fatigue, has been suggested to be affected by injury but may also be implicated in the injury production mechanism. We address two concepts recently described in the motor control literature, variability and abundance, and relate each to neck/shoulder MSD, through a critical review of literature as well as new evidence. These concepts are introduced in relation to the Cinderella hypothesis framework, one of the most recognized pathomechanistic theories underlying the production of MSD. Documented sex differences in motor control and muscle use can also help understand neck/shoulder injury production. Lastly, variability and abundance are presented as two central components of a motor repertoire that can be manipulated to restore normal function after, or optimized to avoid the development of neck/shoulder MSDs.
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,Deficits in Spatial Threshold Control of Muscle Activation as a Window for Rehabilitation After Brain Injury, |
Mindy F. Levin |
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Abstract
Recovery of voluntary control of movement is the main goal of rehabilitation. Despite numerous studies aimed at identifying the most effective rehabilitation interventions, attempts to improve poststroke upper limb recovery remain disappointing: Sensorimotor deficits of the arm and hand persist in a large proportion of stroke survivors (up to 62 %). Indeed, efforts to improve upper limb recovery have been hampered by the lack of understanding of the neural mechanisms underlying spasticity, muscle weakness, and altered kinematic redundancy. Spasticity refers to the presence of hyperactive velocity-dependent stretch reflexes and is associated with disorders of upper motor neurons following central nervous system (CNS) injury such as stroke. Since it is associated with disruption of upper motor neuron function, those with spasticity typically also have weakness and decreased control of voluntary movements. Despite intensive research into these phenomena, the nature of the relationship and neural mechanisms underlying spasticity, weakness, and voluntary control remains unclear. This chapter will describe a new approach to the understanding of this relationship based on deficits in (1) the ability of the damaged CNS to control spatial thresholds (STs) of reflexes and (2) the residual capacity of corticospinal pathways to regulate STs across different regions of the arm workspace in poststroke subjects at rest and during voluntary movement. This approach is driven by recent evidence that, rather than directly specifying motor commands to muscles, the corticospinal system resets STs of reflexes to generate and control voluntary movement.
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,Enhancing Postural Stability and Adaptability in Multiple Sclerosis, |
Richard E. A. van Emmerik,Stephanie L. Jones,Michael A. Busa,Jebb G. Remelius,Julianna L. Averill |
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Abstract
People living with multiple sclerosis (MS) consistently rate balance and gait impairments as having the greatest negative impacts on their quality of life. Our research aims to understand the sensorimotor contributions to balance dysfunction and difficulty with walking in people with MS, with specific attention paid to how fatigue, muscle weakness, and sensory loss interact to limit physical function and mobility. Here, we relate aspects of somatosensory loss and symptomatic fatigue to balance function, and provide new insights in our understanding of the mechanisms of balance and gait dysfunction in MS through the use of novel analytical methods and experimental paradigms. We first review the existing methods and paradigms to assess postural and gait stability in research on MS. Next, we introduce novel measures to assess the stability and adaptability of posture and gait in people with MS that are based on nonlinear and complex systems methods. These novel methods include (1) boundary-relevant measures of postural stability and control (postural “time to contact”), and (2) entropy measures for assessing postural and gait adaptability. These novel methods allow us to differentiate between postural and gait variability caused by dysfunction that may interfere with movement control, and variability that is functional and provides stable and adaptable movement patterns. Finally, we discuss how these methods and paradigms could help to develop innovative treatments for balance and gait dysfunction in people with MS.
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